As a semiconductor device, for example, a display device which displays an image is known. In an active-matrix display device, a thin-film transistor (TFT) is used as a switching element of a pixel. Further, a thin-film transistor is also used as a switching element of a driver which is formed in a frame area (non-display area) on the outside of an active area (display area). As the material of a semiconductor layer of the thin-film transistor, polycrystalline silicon, an oxide semiconductor and the like are used.